Thermostatic switches for high temperature operation are well known in the art. These switches are used in various applications, one of the most notable of which is for appliances, such as electric irons. In an electric iron, the thermostatic switch is responsive to the heat of the soleplate, upon which it is mounted. The switch cycles on and off to maintain the temperature of the soleplate of the iron within the desired set range.
The typical prior art switch structure includes spring members to support the respective electrical contacts. A bimetal element is provided for engaging one of the spring elements as the temperature of the switch rises to break the contacts and interrupt the current to the electric heating element.
In the past, the attempts to design a new type of thermostatic switch have been generally focused on achieving better operating characteristics for a particular type of heat source. One of the most recent improvements in this category is my prior U.S. Pat. No. 4,495,481, issued on Jan. 22, 1985, and assigned to the same assignee as the present invention. In my prior thermodynamic switch, I am successful in alleviating the problems of (1) temperature overshoot that tends to occur on the initial operating cycles of the device, and (2) improving the consistency of operation and thus maintaining a more constant temperature. The switch manufactured in accordance with my '481 invention and patent is proving to be very successful in the particular environment for which it was designed.
More specifically, my previous switch was designed for a particular iron having specific heating characteristics. The line of irons upon which the switch of the '481 invention is utilized exhibits greatly enhanced operational characteristics. As a consequence, the line of irons using my switch are commercially very successful.
Even with the success of the previous switch design, it has been found not to be easily adaptable to other types of irons or other heating appliances, and thus these appliances leave something to be desired in terms of performance. While the switch of my previous design works better than those of the past, the cycling characteristics in other environments than the iron for which it was designed are simply not as favorable as they could be.
It is also a universal problem in the prior art that designing a switch for a particular iron or other appliance generally ups the cost of the switch. Not only is it necessary to order a wide variety of component parts, such as bimetal elements, but also the manufacturing procedures, including the fabricating operations and assembly, must be changed for each switch. If the parts for several switches to fit several different lines of appliances could be standardized and the manufacturing procedures simplified, the cost of switches can be reduced.
Thus, a dual need has been identified for thermostatic switches of the type used in irons or other heating appliances. A switch that can be finely tuned to fit the heating characteristics of different appliances, such as a wide variety of irons, is needed, and especially the need is great for applying this concept while maintaining control of the initial overshoot. In particular, a switch that can be tuned to virtually eliminate temperature overshoot of the appliance and closely regulate and control the operation during use is highly desirable. At the same time, the cost of manufacturing is reduced since the parts and the manufacturing procedures can be better standardized.